## Ch 15 Exercise 3a

$aR \to bP, Rate = -\frac{1}{a} \frac{d[R]}{dt} = \frac{1}{b}\frac{d[P]}{dt}$

Ariana_Kermani_2G
Posts: 10
Joined: Fri Jul 15, 2016 3:00 am

### Ch 15 Exercise 3a

In 20.s, the concentration of nitrogen dioxide, NO2, decreases from 450 mmol/L to 320 mmol/L in the reaction $2NO2\rightarrow 2NO+O2$

(a) Determine the rate of reaction of NO2

Why is the correct answer 6.5 mmol/L x sec and not -6.5 mmol/L x sec? Shouldn't the rate of reaction be negative because NO2 is being consumed? Or is the rate of reaction always supposed to be positive?

Aleena_Sorf_2A
Posts: 22
Joined: Sat Jul 09, 2016 3:00 am

### Re: Ch 15 Exercise 3a

To find the rate of a reactant, we use the following formula:
Rate= - Delta [R] / Delta T

Since the concentration of reactants is decreasing over time, we use a negative in the equation to cancel out the negative value of concentration. In the course reader on page 59, it also says that we want to work with positive reaction rates.

Hope this helps!